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EVALUATION OF THE SODIUM NUTRITION IN THE LAYING HEN 



By 
KRISTINE KRISTINA KUCHINSKI 



A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE 

UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS 

FOR THE DEGREE OF DOCTOR OF PHILOSOPHY 



UNIVERSITY OF FLORIDA 
1998 



ACKNOWLEDGMENTS 

The author greatly appreciates Dr. Robert H. Harms, chairman of her supervisory 
committee. His never ending patience and support were invaluable to this program. He 
always has time for questions and has an endless interest and curiosity for nutritional 
research. The author would also like to thank Dr. Don R. Sloan, Dr. Henry R. Wilson, 
Dr. Ellis Greiner, and Dr. Lee McDowell for their excellent advice and support in this 
program. Appreciation is extended to Gary B. Russell for all the assistance with 
implementation and analysis of these experiments. 

The author also wishes to thank Dr. Ted A. Broome for assistance in surgical 
procedures, analysis of these experiments and manuscript preparation as well as 
tremendous moral support. 

Many thanks to John and Mara Kuchinski for all their support and help in pursuit of 
all my dreams and goals. Thay instilled a firm belief that with faith and work all things are 
possible. 



TABLE OF CONTENTS 

page 
ACKNOWLEDGMENTS ij" 



LIST OF ABBREVIATIONS. 



REFERENCES 

BIOGRAPHICAL 
SKETCH 



IV 



ABSTRACT v 

CHAPTERS 

1 INTRODUCTION j 

2 REVIEW OF LITERATURE 2 

3 MANIPULATION OF DIETARY INGREDIENTS IN ADDITION 

TO SODIUM FOR SHORT PERIODS OF TIME 6 

4 RE-EVALUATION OF THE SODIUM REQUIREMENT 

OF THE COMMERCIAL LAYING HEN 20 

5 SIGNS OBSERVED IN COMMERCIAL LAYING HENS 

FED A LOW SODIUM DIET 32 

6 DETERMINATION OF CYCLICITY OF PLASMA SODIUM 46 

THE ABILITY OF HENS TO REGULATE CHLORIDE INTAKE 
WHEN OFFERED SODIUM FROM SODIUM CHLORIDE AND 
SODIUM BICARBONATE 5! 

8 SODIUM REQUIREMENT FOR BROILER BREEDER HENS.... 56 

9 SUMMARY AND CONCLUSIONS 66 



70 
74 



iii 



LIST OF ABBREVIATIONS 



BW Bodv Weight 

BWC Body Weight Change 

EC Egg Content^ (egg production X(whole egg weight - shell 

weight)) 

EM Egg Mass = (egg production X whole egg weight) 

EP Egg Production 

FC Feed Consumption 

FI Feed Intake 

g/b/d grams per bird per day 

SCWL Single-comb White Leghorn 

WG Weight Gain 

WL Weight Loss 



IV 



Abstract of Dissertation Presented to the Graduate School of the University of Florida in 
Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy 

EVALUATION OF THE SODIUM NUTRITION IN THE LAYING HEN 

By 

Kristine Kristina Kuchinski Broome 

May, 1998 

Chairman: Robert H. Harms 

Major Department: Animal Science (Poultry) 

In order to maximize production and profits, laying hens are currently fed according 
to the daily nutrient requirements at their stage of growth or production. An experiment 
was conducted to evaluate aspects of ingredient and nutrient manipulation, emphasizing 
sodium, to evaluate effects on the laying hen. Hens were fed a complete layer diet or a diet 
consisting of a combination of corn, limestone, dicalcium phosphate, microingredients or 
salt. The use of reduced nutrient diets resulted in reduced feed consumption within 2 days 
whereas egg production (EP) was not reduced until day 6 and follicular regression occurred 
after day 7. 

Two experiments were conducted to re-evaluate the sodium (Na) requirement of the 
commercial layer and broiler breeder. Broken line regression of Na intake on egg content 
and EP indicated a daily requirement of 1 13 mg/h/d and 99 mg/h/d, respectively, for the 
layer. The daily requirement for maximum production was 1 13.8 and 96 mg and the 
requirement for egg mass was 105 and 100 mg in experiments 1 and 2, respectively, for 
the broiler breeder. Hens fed a low salt (0.02% Na) diet had significantly lower serum Na 
and higher potassium levels. In the fourth experiment, hens receiving a low salt diet 
exhibited reduced egg production within 5 d. Ovarian follicles continued to develop until 



the day the last egg was laid, then the follicles began to regress. In the fifth experiment, 
hens were fed a low Na diet and serially sampled to determine if plasma Na cycled during 
the production of an egg. Insufficient evidence was found to prove cyclicity of plasma Na. 
In the last experiment, hens were offered a choice of diets with NaCl or NaHCOj to 
determine if the hen would select for chloride intake. It did not appear that hens were able 
to adjust consumption of the two diets in order to balance the nutrients, but egg shell 
quality was improved in the hens consuming the NaHCO? diet. 






vi 



CHAPTER 1 
INTRODUCTION 



In addition to proteins, carbohydrates, fats, and certain vitamins, there are other 
nutrients necessary to support maintenance of life, production of meat and eggs, and 
reproduction. These include minerals such as sodium and chloride. All animals have a 
requirement for sodium and chloride (salt) in their diet Mammals crave salt and will 
actively seek it out along with other minerals. This behavior has been observed in some 
species of wild birds. (Munn, 1994). 

Commercial hens produce eggs at a high rate but over time the eggshell quality and 
rate of production may decline. When a hen molts, egg production ceases and a "rest" is 
allowed. When the molt is completed, the hens will return to production at a higher rate 
and with improved eggshell quality compared to before the molt. Recycling or force 
resting a flock of laying hens is a management tool to extend a laying flock's performance. 
The decision to rest a flock is based on economic conditions in the egg industry, including 
egg prices, cost of replacement pullets, and feed costs, which may cause the producer to 
maintain a flock in production for longer than one year. 



CHAPTER 2 
LITERATURE REVIEW 



Considerable disagreement exists regarding the actual requirement for sodium 
chloride in poultry diets. Early work by Halpin et al. (1936) reported that growth rate of 
chicks was improved and egg production occurred earlier for hens fed 1% salt as opposed 
to those fed 2.0% and 0.5% salt. This value of 1.0% was also reported by Barlow et al. 
(1948). Using chicks, Heuser (1952) found that the ingredients in an average practical 
diet met the chicks sodium needs, but that added salt improved growth rate. McWard and 
Scott (1961) found that 0.20% salt in the diet was needed for chick growth. Egwuatu et al. 
(1983) studied salt deficiency in chicks and found that bony abnormalities decreased in 
chicks with increasing salt levels starting from a basal diet with 0. 103% salt. In the 1971 
National Research Council report, the hen's sodium chloride requirement is listed as 0.3% 
or 0.15% sodium in the diet. Later, NRC (1984) suggested the requirement for Na as 165 
mg per day per hen but reduced the suggested requirement to 150 mg per hen per day in 
1994. Cohen et al. (1972) found a requirement of 0.13% sodium or 0.32% sodium 
chloride. Reid (1977) investigated the effects of housing on the Na requirement and 
reported that hens in conventional housing required 141 mg per day per hen and in 
evaporative cooling housing they required 149 mg per hen per day. Burns et al. (1952) 
looked at a variety of parameters affecting Na and found 0.24% was adequate for body 
weight maintenance, egg production and hatchability in commercial layers. They also 
found that chicks from sodium deficient hens also had a higher sodium requirement. Burns 
explained that much of the previous work had attempted to determine optimum not 
minimum levels. Dilworth et al. (1972) compared the sodium requirement of hens in 



cages versus those on the floor and found the floor birds had a lower dietary requirement. 
This was explained by the recycling of sodium when the hens consumed litter and fecal 
matter. 

Hurwitz et al. (1973) suggested that the requirement of one nutrient may depend on 

the level of another nutrient The varying levels of sodium, potassium and chloride were 

found to affect the plasma values of each other and bicarbonate levels as well. The 

variation in salt requirement as influenced by chloride, potassium, calcium, phosphorus 

and manganese was reported earlier by Nesheim et al. (1964) and Slinger et al. (1950). 

These interrelationships were further explored by Sauveur and Mongin ( 1978) who found 

that an optimum level of sodium, chloride or potassium cannot be determined independent 

of the levels of the other two. Damron and Harms ( 1980) looked at how the interactions 

of salt with calcium and phosphorus affected egg production and found improved egg 

production with increasing salt levels up to 0.70% supplemental salt Christmas and Harms 

(1982) found that high levels of sodium fed with low levels of chloride depressed egg 

production, feed efficiency, and egg weight. Junqueira et al. (1984) found that 1.11% 

sodium chloride supplementation decreased egg production when fed in addition to 0.3% 

P and even more so with 0.6% P. Pimentel and Cook ( 1987) stressed the importance of 

other response criteria in determining the sodium chloride requirement for chicks. They 

found that chicks fed less than 0.14% sodium in the diet had a suppressed humoral 

response and that increasing chloride levels in diets fed to chicks on sodium deficient diets 

depressed antibody responses even further. 

Interrelationships have been found between sodium, chloride and potassium. 
Nesheim et al. (1964) found excess chloride (0.81%) depressed growth in the chicks 
unless balanced with equimolar levels of sodium or potassium. Excess sodium (0.89 and 
1.05%) was also detrimental unless balanced with a high level of chloride. 



Production was observed to drop from 70% to 0% over 21 days in an apparently 
healthy commercial flock of Leghorn hens (Nesbeth, 1976a). Investigation determined the 
cause to be the accidental omission of salt from the diet . The hens recovered completely 
within 13 days of receiving an adequate diet. The potential use of a no added salt diet for 
forced resting hens was recognized and several investigators began to evaluate 
manipulation of dietary salt levels for this purpose. 

Other methods of forced resting or forced molting as previously known have been 
shown to improve flock performance. Fasting has been a widely used and proven effective 
method of forced resting (Len et al., 1964; Noles, 1966; Swanson and Bell, 1974; Roland 
and Brake, 1982). High dietary zinc has also been utilized to induce molting (Shippee et 
al., 1979; Palafox and Ho-A, 1980) as has restriction of dietary calcium (Whitehead and 
Shannon, 1974; Naber et al., 1980). Feeding high levels of iodine has also been shown to 
induce a rest (Wilson et al. 1967). The above methods may be unacceptable from an 
animal welfare concern and the fasting methods generally employ alterations in photoperiod 
which may be difficult in some situations. Therefore, a low sodium diet offers the appeal 
of avoiding most of these pitfalls. Many researchers have examined the potential use of a 
low sodium or no added salt diet for use as a forced resting procedure. Whitehead and 
Shannon (1974) fed diets with sodium levels of 0.038% and found that when fed prior to 
onset of lay this diet reduced production to a very low level. When fed to older birds of 
varying ages, the diet reduced production to very low rates. Nesbeth et al (1976 a,b) found 
that a level of 0.017% sodium or 0.044% sodium chloride induced an effective rest in 
laying hens and the birds returned to production in 16 and 12 days, respectively. These 
researchers also noted that feed intake decreased within 24 hours when hens were fed a salt 
deficient diet. Monsi and Enos (1973) attempted to evaluate the sensitivity and 
performance of hens to low salt levels in practical diets. Diets had 0, 0. 125, and 0.250% 
salt added. The birds dramatically reduced egg production in the 0% added salt group with 
the two other treatments following suit within 4 to 5 weeks. These researchers found egg 



weight, shell thickness, shell strength and albumen height unaffected by the treatments. 
Additional studies have been done that confirm that low sodium diets dramatically reduce 
egg production with no additional deleterious effects (Begin and Johnson, 1976; Naber et 
al., 1984; Harms, 1991). A low sodium diet forced resting has been compared to the other 
methods of forced resting-fasting and high dietary zinc-and found to be comparable in 
postmolt performance parameters (Berry and Brake, 1985). 

The effect of the low salt diet has been shown to be specifically due to the sodium 
level. Harms ( 1991) fed diets with no added salt, no added salt but sodium supplemented, 
and no added salt but chloride supplemented. He found the diets with no added salt and no 
added salt with no sodium supplementation reached zero production quickly. Only a few 
hens supplemented with chloride demonstrated sensational production drops. Hens in the 
no added chloride group also had increased mortality of 20%. Berry and Brake (1985) 
hypothesized that effects of the low sodium diets may not be due to a sodium deficiency per 
se, but to deficiencies of nonmineral nutrients brought about by the sodium deficiency. 
This may occur because sodium dependent carrier proteins in the intestine may be 
responsible for absorption of hexoses and certain amino acids. Without a sodium and a 
sugar binding the carrier protein concurrently, then tranport does not occur (Baker, 1983). 



CHAPTER 3 

MANIPULATION OF DIETARY INGREDIENTS IN ADDITION TO 

SODIUM FOR SHORT PERIODS TIME 



Introduction 

In order to maximize production and profits, laying hens are currently fed according 
to the daily nutrient requirements at their stage of production throughout the laying cycle 
(Harms, 1981b). To safeguard against deficiencies, margins of safety are built into diets 
resulting in the feeding of levels above the requirement. After reaching maturity, stores of 
minerals are laid down in bone and excess energy in fat. When the diet fails to meet the 
hen's needs, these reserves are utilized and production maintained. When nutrient intake 
remains deficient, production will fall. By requiring the hen to make use of this pool of 
nutrients in a short period of time prior to market, feed costs can be reduced while 
production is maintained. However, information is needed to determine how long nutrient 
intake can be reduced before loss of production occurs. 

In addition to manipulation of the Na level in the diet, previous work has shown 
manipulation of other ingredients, such as calcium fed at increased levels (Damron and 
Harms, 1980) can significantly decrease feed intake. Dietary manipulation might be 
utilized to decrease feed intake and reduce costs in the last days prior to marketing spent 
hens. The most economical solution would be dietary deletions resulting in lower 
consumption of a less expensive feed without a significant decrease in production. Some 
preliminary work has been done using a "wring-out" diet (Schutze, 1992). 



This study was undertaken to evaluate the effect of the elimination of certain 
ingredients from the diets of laying hens less than one week from market Decreased 
production was expected and the goal was to determine the length of time these diets could 
be fed and still provide an economical return through decreased feed intake of a less 
expensive feed. 

Materials and Methods 

Two experiments were conducted using Hy-Line W36 hens, 60 and 64 weeks of 
age. The hens were individually caged in open sided houses and exposed to a 15 hour 
light:9 hour dark photoperiod. Egg specific gravity was determined by suspending eggs in 
16 salt solutions with specific gravities ranging from 1.060 to 1.0975 in increments of 
0.0025 for Experiment 1 and in increments of 0.0025 ranging from 1.070 to 1.090 in 
Experiment 2. Egg production was recorded daily. At termination, hens were euthanized 
via cervical dislocation, necropsied, and their ovaries were weighed. Ovaries were 
examined for evidence of active and regressing follicles. 

Composition of diets and calculated nutrient analyses are presented in Tables 3-1 
and 3-2 for Experiment 1 and 2, respectively. Protein decreased and energy increased as 
the percentage of corn increased in the diet and phosphorus was lower and calcium higher, 
in all the treatment diets when compared to the control diet 

Experiment 1 

Each of the four treatment groups consisted of four replicates of 10 individually 
caged hens. Hens were weighed the day before initiation of the trial and on the day of 
termination at day 1 1. The four dietary treatments (Table 3-1) were: 1) a complete diet for 
hens near the end of the first cycle; 2) a diet containing corn, calcium (4.5%), 
microingredients, and salt; 3) the same as diet 2 without microingredients; and 4) the same 



8 

as diet 2 without microingredients and salt Feed intake was determined at the end of day 
seven and day 11. All eggs were collected, weighed and specific gravity determined for 
the first eight days of the experiment At necropsy the left tibia was collected, cleaned, 
defatted, and oven dried. Breaking strength was evaluated using a FTC Texture Test 
System apparatus (Rowland et al., 1967). 

Experiment 2 

The five diets were fed (Table 3-2): 1) a complete diet for hens less than six weeks 
to market; 2) a diet containing corn, calcium (4.5%), P, microingredients, and salt; 3) the 
same as diet 2 without P; 4) a diet containing corn, calcium (6%), P, microingredients and 
salt; and 5) the same as diet 4 without P. Each diet was fed to six replicates of 10 
individually caged hens. Feed was weighed and feed intake measured at day 2, 4, and 7. 
Eggs were collected from each hen, weighed and specific gravity determined daily. Body 
weight change was not measured. The experiment was terminated on day 7. Data were 
analyzed utilizing an ANOVA and Duncan's multiple range test to identify significant 
differences among treatments (Duncan, 1955; SAS, 1990). 

Results and Discussion 

Hens given diets 2, 3 and 4 in Experiment 1 consumed approximately one third less 
feed when compared to the intake of hens given diet 1 (Table 3-3). Feeding diet 4, the diet 
with no added salt, resulted in no further significant decrease in feed intake compared to 
diets 2 and 3. This was unexpected as the removal of salt alone from the diet results in a 
significant decrease in feed intake. Feed consumption of control hens was greater during 
days 8-11 than days 1-7 (Table 3-3). We have no explanation for this increase. In 
Experiment 2, (Table 3-4) feeding the reduced nutrient diets resulted in a 20-24% reduction 
in feed intake for days one and two, 17-26% reduction for days three and four, and 23- 



33% reduction for days five through seven when compared to feed intake of hens fed diet 
1. Feeding diet 5, with 6% calcium and no added phosphorus, consistently produced the 
lowest feed intake. Feed intake was not decreased proportionately to the energy level in the 
diet. The hens consuming the reduced nutrient diets did not consume as much energy as 
hens on diet 1 (Table 3-5). Additionally, hens receiving the reduced nutrient diets did not 
regulate intake equal to the protein, calcium or phosphorus intake of hens consuming diet 
1. The removal of salt from the feed did not cause an additional decrease in feed intake. 
The identity of the nutrient which affected feed intake is not apparent. 

Feeding reduced nutrient diets significantly reduced EP after day 6 (Tables 3-6 and 
3-7). At day 6, EP began to decrease at a rapid rate in both experiments. The cost of feed 
ingredients would determine how much of a decrease in production would be offset 
economically by the decreased feed costs due to decreased intake. 

Egg weight immediately decreased significantly in both experiments (Tables 3-6 
and 3-7) when hens were fed the reduced nutrient diets. This decrease in egg weight may 
be due to the lower protein intake provided in the experimental diets. Experiment 1 was 
conducted in hot weather and Experiment 2 was conducted in cold weather. Therefore, 
eggs were heavier in Experiment 2. 

Egg specific gravity was significantly reduced during the first five days in 
Experiment 1 (Table 3-6) when the reduced nutrient diets were fed. However, this 
difference decreased with time and specific gravity improved beyond the initial values. 
This improvement in specific gravity after day 5 may be explained by the concurrent 
decrease in EW. Specific gravity was only reduced when hens were fed diet 2 in 
Experiment 2. No shell-less eggs were laid in either experiment. 

Ovary weight was significantly reduced by day 1 1 in Experiment 1 and day 7 in 
hens fed the reduced nutrient diets (Tables 3-8 and 3-9). At necropsy, all hens fed the 
reduced nutrient diets in both experiments showed evidence of follicular regression except 
one hen in Experiment 1. 



10 



Hens fed the control diet had active follicles with no signs of regression. There 
was no mortality during the two experiments. All hens appeared normal during necropsy at 
the termination of both experiments. Body weight loss in Experiment 1 and 2 was 
significantly greater for hens fed the reduced nutrient diets as compared to hens fed the 
control diet There was no significant difference in bone breaking strength among the 
groups of hens. 










Corn 


73.76 


87.25 


SBM (48%) 


15.15 





Limestone 


9.46 


11.84 


Dical Phos A 


0.69 





DLMet 


0.02 





Microingred^ 


0.5 


0.5 


Salt 


0.41 


0.41 


Calculated Analysis 






Protein (%) 


13.55 


6.97 


Calcium (%) 


3.81 


4.52 


Phosphorus (%) 


0.43 


0.24 


Sodium (%) 


0.18 


0.18 


Metabolizable 


2867 


2956 


Energy (kcal/kg) 







87.75 88.16 


11.84 11.84 






0.41 



7.01 7.04 

4.52 4.52 

0.25 0.25 

0.18 0.02 

2973 2987 



A Dicalcium phosphate (18.5% phosphorus and 21% calcium). 

B Provides per kg of diet: 6,600 IU vit A; 2,200 ICU vit D3; 2.2 menadione 
dimethylpnmidinol bisulfite; 4.4 mg riboflavin; 39.6 mg niacin; 13 mg pantothenic acid- 
500 mg choline; 0.02 mg vit Bi 2; 125 mg ethoxyquin; 60 mg Mn; 50 mg Fe- 60 me Or 
0.2mgCo;l.lmgI;35mgZn. e ' 



12 



TABLE 3-2. Composition of diets (Experiment 2) 









Diet 






Ingredient 


1 


2 


3 


4 


5 




(%) 






Corn 


73.76 


87.00 


87.75 


83.05 


83.30 


SBM (48%) 


15.12 














Limestone 


9.46 


11.40 


11.84 


15.35 


15.79 


Dical Phos A 


0.69 


0.69 





0.69 





DLMethionine 


0.06 














MicroingredB 


0.50 


0.50 


0.50 


0.50 


0.50 


Salt 


0.41 


0.41 


0.41 


0.41 


0.41 


Calculated Analysis 












Protein (%) 


13.56 


6.95 


6.97 


6.64 


6.66 


Calcium (%) 


3.81 


4.51 


4.52 


6.01 


6.02 


Phosphorus (%) 


0.43 


0.37 


0.24 


0.36 


0.23 


Sodium (%) 


0.18 


0.18 


0.18 


0.18 


0.18 


Met Energv 


2867 


2948 


2956 


2814 


2822 


(kcal/kg) 













A Dicalcium phosphate (18.5% phosphorus and 21% calcium). 

B Provides per kg of diet: 6,600 IU vit A; 2,200 ICU vit D 3 ; 2.2 menadione dimethylprimidinol 
bisulfite; 4.4 mg riboflavin; 39.6 mg niacin; 13 mg pantothenic acid; 500 mg choline- 02 mg vit 
B 12; 125 mg ethoxyqum; 60 mg Mn; 50 mg Fe; 60 mg Cu; 0.2 mg Co; 1.1 mg I; 35 mg Zn. 












13 



TABLE 3-3. Feed intake of hens fed various reduced nutrient diets (Experiment 1). 



D"* Feed Intake 

Day 1-7 Day 8-11 

(g/h/d) 2 

Contro1 84.9 ± .8 a 94 1 ± 2 0* 

Com + Ca +S+M1 61.1 ± 1.4b 392 ±1 2*> 

Corn + Ca + S 55 3 ± x 6 bc ^j ± j 2 b 

Com + Ca 52.4 ± 2.7c 60.1 ± 13b 



a_c Means within a column with no common superscript are significantly different (P < 
ingredients used in diet: Ca = 4.5% Ca from limestone, M =microingredients and S = 
2 x ± SEM. 



14 



TABLE 3-4. Feed intake of hens fed various reduced nutrient diets (Experiment 2) 



Diet 1 



Control 

Corn+4. 5%+Ca+P+M+S 
Corn +4.5% Ca+M+S 
Corn +6% Ca + P + M + S 
Corn +6% Ca + M + S 



Feed Intake 
Days 1-2 2 Days 3-43 



130.0 ±2.4a 
103.1±3.ic 
104.4±2.9c 
116.1±4.1 b 
99.0±1.3 C 



(g/hen/day) 3 
116.8±L7 a 

93.4±3.7 bc 

89.3±1.8 C 

97.0±1.7b 

86. 1±2.8 C 



Days 5-7 4 



95.8±3.0a 
71.0±1.8b 
64.9±1.6 C 
74.4±1.3 b 
63.9±1.8 C 



1 Ingredients used in diet Ca = limestone; M =microingredients; S = salt P =dicalcium 
phosphate. 

2 Includes feed placed in troughs at 2100 h on day before experiment started and weighed 
back at 0900 h on day 3. 

3 Includes feed consumed from 0900 h on day 3 until 0900 h day 5. 

4 Includes feed consumed from 0900 h on day 5 until 1600 h day 7 

5 x ± SEM. 

<*-CMeans within a column with no common superscript are significantly different (P <. 



15 



TABLE 3-5 Daily intake of calcium, phosphorus, protein, and energy when hens were fed 
various diets 



Dailv Intake 


Diet A 
Control 


Ca 

(g) 

3.36 


P Protein 
(g) (g) 
Expenment 1 
0.379 12.0 


Energy 
(kcal) 

253 


Corn + Ca +S+M 


2.73 


0.145 


4.2 


179 


Corn + Ca + S 


2.64 


0.146 


4.1 


174 


Corn + Ca 


2.54 


0.140 


3.9 


168 


Control 


4.25 


Experiment 2 
0.480 15.1 


320 


Corn+4.5%+Ca+P+M+S 


3.91 


0.320 


6.0 


255 


Corn +4.5% Ca+M+S 


3.76 


0.200 


5.8 


246 


Corn +6% Ca + P + M + S 


5.50 


0.329 


6.1 


257 


Corn +6% Ca + M + S 


4.98 


0.190 


5.5 


233 



A Ingredients used in diet: Ca = limestone; M =microingredients; S = salf P =dicalcium 
phosphate. 



16 



TABLE 3-6. Performance of hens fed various reduced nutrient diets (Experiment 1) 



Diet A 


1-5 


Davs 
6 


7 


8 


Hen-day Egg Production (%) 


Control 

Com+Ca+M+S 
Com + Ca + S 
Com + Ca 


69.5±2.1 ab 
75.0±2.1 ab 
66.5±4.3 ab 
61.0±5.5 b 


75.0 ±6.53 

62.5 ±7.5a 

50.0 ±4.2** 

30.0 ±10.0° 

Egg Weight (g) B 


85.0 ±2.93 

47.5 ±4.83 

37.5 ±11.2** 

25.0 ±6.5* 


77.5 ±4.8* 
36.7 ±5.8* 
30.0 ±6.2* 
17.5 ±8.5* 


Control 

Com+Ca+M+S 
Com + Ca + S 
Com + Ca 


62.0±0.6 a 
59.5±0.6 b 
58.9±0.5 b 
59.2±0.6 b 


61.1 ±0.8 a 

60.2 ±1.0* 
58.7 ±1.2ab 

57.2 ±1.4 b 
Specific Gravitv B 


60.1 ±0.8 a 
57.1 ±1.3 b 

58.1 ±1.0* 

57.2 ±1.3* 


59.6 ±0.9 
59.8 ±2.1 
59.3 ±1.3 
56.2 ±1.7 


Control 

Com+Ca+M+S 
Com + Ca + S 
Com + Ca 


789±7 a 
756 ±6 b 
748 ±6 b 
739 ±6 b 


760 ±8 
747 ±10 
760 ±10 
730 ±20 


803 ±8 a 
750 ±9 b 
730±17 b 

774 ±27* 


811 ±ll a 

777 ±14* 
758 ±22 b 
748±18 b 



A Ingredients used in diet: Ca = limestone; M =microingredients; S = salt; P =dicalcium 
phosphate. 

B x ± SEM. 

a_c Means within a column with no common superscript are significantly different (P < 



17 



TABLE 3-7. Performance of hens fed various reduced nutrient diets (Experiment 2) 



Diet 1 


1-5 


Days 

6 


7 


Hen-dav Egg Production (%) 2 


Control 


73.4 ±5.6 


81.5 ±6.02 


77.3 ±10.93 


Com+4.5%+Ca+P+M+S 


72.5 ±3.7 


58.3 ±8.4 ab 


39.3 ±5.6 b 


Corn +4.5% Ca+M+S 


66.5 ±2.9 


61.6 ±5.0 ab 


40.8 ±5.2 b 


Corn +6% Ca + P + M + S 


66.9 ±5.7 


56.8 ±10.9 b 


44.4 ±11. 6 b 


Corn +6% Ca + M + S 


70.9 ±2.2 


55.6 ±10.4 b 

Egg Weight (g)2 
66.7 ±0.8 a 


43.9 ±5.3 b 


Control 


67.0 ±0.73 


68.0 ±0.93 


Com+4.5%+Ca+P+M+S 


63.6 ±0.6 bc 


61.4 ±0.9° 


63.3 ±1.4 b 


Corn +4.5% Ca+M+S 


63.1 ±0.6 C 


60.9 ±1.0° 


61.4 ±1.0 b 


Corn +6% Ca + P + M + S 


65.2 ±0.5 b 


64.5 ±0.9 ab 


63.2 ±0.9 b 


Corn +6% Ca + M + S 


64.3 ±0.5bc 


63.1 ±0.9^ 
Specific Gravitv 2 


62.7 ±1.0 b 


Control 


804±5 ab 


832 ±7 


816 ±5 b 


Corn+4.5%+Ca+P+M+S 


795 ± lib 


820 ±10 


837±10 ab 


Corn +4.5% Ca+M+S 


813 ±5a 


815±11 


853±10 ab 


Corn +6% Ca + P + M + S 


807 ±8 ab 


839 ±9 


828 ±ll& 


Corn +6% Ca + M + S 


819 ±7 a 


839 ±10 


859±12 a 



1 Ingredients used in diet: Ca = limestone; M =microingredients; S = salf P =dicalcium 
phosphate. 

2 x ± SEM. 

a-CMeans within a column with no common superscript are significantly different (P ^ 



18 









TABLE 3-8. Ovary weight, body weight, and bone breaking strength (tibia) of hens fed 
reduced nutrient diets for 11 days (Experiment 1) 



Diet 1 


Ovary Weight 
(g) 2 


Body Weight Loss 
(g) 2 


Bone Breaking 
Strength 

(kg/g) 2 


Control 


40.7 ±4.2 a 


37 ±25* 


2.8±0.1 a 


Corn + Ca +S+M 


18.0 ±3.9 b 


189±32 b 


3.1 ±0.1* 


Corn + Ca + S 


14.3 ±4.4 b 


197±34 b 


3.1 ±0.1* 


Corn + Ca 


10.2 ±1.2 b 


228±38 b 


2.8±0.1 a 



1 Ingredients used in diet Ca = limestone; M =microingredients; S = salt; P =dicalcium 
phosphate. 

- x ± SEM. 

a - b Means within a column with no common superscript are significantly different (P ^ 



19 



TABLE 3-9. Ovary weight of hens fed reduced nutrient diets for 7 days (Experiment 2) 



Diet 1 Ovarv Weight 2 
- (g> 



Control 



48.2 ±2.7 a 

Corn+4.5%+Ca+P+M+S 25 8 ±3 5 b 

Corn +4.5% Ca+M+S 23 1 ±4 4 b 

Corn +6% Ca + P + M + S 25 8 ±6 7 b 

Corn +6% Ca + M + S 23 5 ±4 3 b 



1 Ingredients used in diet Ca = limestone; M =microingredients; S = salt; P =dicalcium 
phosphate. 

"x± SEM. 

a " b Means within a column with no common superscript are significantly different (P «s 



CHAPTER 4 

RE-EVALUATION OF THE SODIUM REQUIREMENT OF THE 

COMMERCIAL LAYING HEN 



Introduction 

The National Research Council (1994) suggests 150 mg/hen/day as the sodium 
requirement for the commercial laying hen. The NRC (1984) had previously suggested 
165 mg per day. Reid ( 1977) reported that hens in conventional housing required 141 mg 
Na per day and those in evaporative cooled houses required 149 mg per day. Water 
supplied to those hens contained 75 ppm Na. However, water intakes were not 
monitored. Based on previous data, Harms ( 1981b) suggested a daily intake of 170 mg Na 
which included a margin of safety. Therefore, the present study was conducted to further 
evaluate the sodium requirement of the Leghorn hen. 



Materials and Methods 

Experiment 1 

Three hundred twenty 36-week old Hy-Line W36 hens were used to determine 
their sodium requirement. A corn-soybean basal diet (Table 4-1) was used which 
contained 0.056% Na The hens were maintained in individual cages in replicates of 5 
hens, and 8 replicates were fed each of the 8 experimental diets. The 8 diets contained Na 
levels of 0.056, 0.078, 0.100, 0.122, 0.144, 0.166, 0.188, and 0.210%. Sodium 



20 



21 

increases were made by substituting NaCl for com. Chloride requirement was met by all 
diets. The drinking water contained 9 ppm Na 

The experimental diets were fed for 8 wk; the first 2 wk were considered as a 
depletion period and wk 3 through 8 were used to measure treatment effects. Feed 
consumption (FC) was measured by replicate at two-week intervals; however, only the data 
for the last 6 wk were evaluated. Daily egg production (EP) was recorded for each hen; 
however, data by replicate were used for analysis. One egg from each hen was weighed 
during the last 2 d of each week. Eggs were broken out, shells washed under a small 
stream of water, air dried and then the shell plus membrane were weighed to the nearest 
0. 1 g. Egg mass (EM) was calculated by multiplying egg weight (EW) by EP. Egg 
content (EC) was calculated by multiplying EP by (EW - shell weight). Sodium intake was 
obtained by multiplying FC by Na content of the diet. Body weight change (BWC) was 
determined by subtracting initial weight from final weight 



Experiment 2 

A second experiment was conducted using 40-week old Hy-Line W36 hens to 
determine the sodium requirement for egg production, fertility and hatchability. The corn- 
soybean basal diet was the same as used in Experiment 1 (Table 4-1) and contained 
0.056% Na Eight replicates of 5 individually caged hens were fed each of the 6 
experimental diets. The 6 diets contained sodium levels of 0.056, 0.078, 0. 100, 0.122, 
0. 144, and 0. 166% Na. NaCl was used as the sodium source in the diets. Sodium 
increases were made by substituting NaCl for corn. Drinking water contained 9 ppm Na 

The experimental diets were fed for 6 wk; however, the first 2 wk were considered 
a depletion period and wk 3 through 6 were used to measure treatment effects. Daily egg 
records were kept and replicate data were used for analysis. Hens were artificially 
inseminated with pooled semen from Hy-Line W36 males on the first day of wk 1 through 



22 

5. Insemination was not done at the beginning of week 6 in order to evaluate duration of 
fertility. Egg collection began 2 d after the initial insemination and eggs were set weekly. 
Eggs were candled weekly to remove infertile eggs and dead embryos. Body weights of 
the hens were measured on days and 28. Feed consumption for each replicate was 
measured every 14 d. 

The data were subjected to a one-way ANOVA (SAS, 1990). Replicate data were 
used for EP, FC and Na intake. Individual data were used for EM, EC and BWC. The 
residual means square was used as the error term and Duncan's multiple range test ( 1955) 
to determine significant differences between treatment means. Broken line regressions 
were calculated relating EC (Experiment 1) or EP (Experiment 2) to sodium intake (Noll 
and Waibel, 1989) . 

RESULTS AND DISCUSSION 

Experiment 1 

Reducing the level of sodium in the diet below 0. 122% (1 14mg/d) resulted in a 
significant decrease in EP (Table 4-2). A significant reduction in EP during the first 2 wk 
was followed by a further decrease during the third week and then it was fairly constant for 
the remainder of the 8 wk experiment The reduction in EP was a result of a reduction in 
sequence length and an increase in pauses, when hens did not lay an egg. EP was not 
significantly reduced until the daily intake of sodium was reduced from 1 14 to 87 
mg/hen/day. None of the hens molted during the experiment. 

Egg weight was significantly reduced when hens had a daily intake of 29 or 48 mg 
Na per day (Table 4-2). The reduction of EP along with reduced EW resulted in a large 
decrease in EC when the daily Na intake was reduced below 1 14 mg per day. The effects 
on EC were observed in wk 2 and thereafter (Figure 4-1) with the lowest EC occurring in 
wk 3 or 4. The Na intake/g/EC decreased significantly as the daily Na intake/hen 



23 

decreased. Feed consumption significantly decreased during the first 2 wk the hens were 
fed the low sodium diets (Table 4-2). Body weight change decreased as the level of sodium 
decreased in the diet (Table 4-2). Hens consuming 87 mg Na per day or less lost weight 

Broken line regression of EC and EP on sodium intake indicated a daily 
requirement of 1 13.4 mg (R 2 = .98) and 104.6 mg(R2=.98), respectively. This is 
considerably lower than suggested by NRC ( 1994) and the 170 mg/day suggested by 
Harms ( 1981b). The water contained only 9 ppm Na and therefore, the sodium in the 
water did not make a meaningful contribution. 



Experiment 2 

Egg production decreased dramatically (Figure 4-2, Table 4-3) from wk 1 to 3 in 
the hens consuming 53.3 or 34.8 mg Na/d/hen. Egg production continued to decrease 
through wk 4 for hens consuming 53.3 mg Na then began to increase slightly as did that 
for hens consuming 34.8 mg Na but neither treatment returned to a level of EP comparable 
to that of hens with a daily sodium intake of 91. 1 mg or above. Feed consumption in the 
groups consuming 34.8 or 53.3 mg Na/d also decreased significantly (Table 4-3) in the 
first 2 wk and remained low throughout the remaining weeks. Body weight change 
decreased as the level of sodium in the diet decreased. Birds consuming 91. 1 mg of 
sodium or less per day lost weight This agrees with the results found in Experiment 1. 
Egg production was regressed only instead of EC and EP because the eggs were set for 
hatchability in Experiment 2. Broken line regression indicated a daily requirement of 99 
mg Na per day which was lower than the NRC ( 1994) requirement and the requirement 
found in Experiment 1. 

This decrease in EP may be explained by a decrease in sequence length of the hens 
on lower levels of sodium. This is illustrated by Figure 4-3 indicating a significant 
decrease in sequence length in hens fed the 2 lowest levels of sodium. The more frequent 



24 

pauses resulted in lower overall EP. The pause length between sequences remained at one 
day for all treatment groups. 

Fertility was not significantly affected by sodium intake, though the groups 
receiving lower levels of sodium had numerically lower fertility that approached 
significance (Table 4-4). Hatchability of fertile eggs and hatchability of all eggs set of 
hens receiving lower levels of sodium were significantly lower than those for the other 
groups. This may have been somewhat affected by low EP in these treatments. The 
effect on fertility, fertile hatch and total hatch was similar to that seen in the turkey (Harms 
et al. 1985). Duration of fertility, defined by the number of days between last artificial 
insemination and last fertile egg, was the same in all treatment groups at approximately 1 1 
days (Table 4-4). 












25 



TABLE 4-1. Composition of the basal diet 



Ingredient 

Corn 

Soybean meal (48.5%) 

Limestone 

Dicalcium phosphate (18.5% P, 21% Ca) 

Micromgredients 2 

Salt 

DL Methionine 


Content (%) 




67.42 
21.51 
8.68 
1.56 
0.60 
0.09 
0.14 





1 Contained 0.056% sodium, the lowest dietary level that was fed 

2 Supplied per kilogram of diet: vitamin A, 6,600 IU; vitamin D3, 2,000 ICU; menadione 
dimethylpynmidinol bisulfite, 2.2 mg; riboflavin, 4.14 mg; pantothenic acid 13 2 mg- 
niacin, 39.6 mg; vitamin B 12 , 0.022 mg; choline chloride, 499.4 mg; ethoxyquin 23 
mg; manganese, 60 mg; iron, 50 mg; copper, 6 mg; iodine, 1.1 mg; zinc, 3*5 me' 
selenium, 0.1 mg. 



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CHAPTER 5 
SIGNS OBSERVED IN COMMERCIAL LAYING HENS FED A LOW 

SODIUM DIET 

Introduction 

Since the early 1970*s when the cessation of laying caused by a sodium defiency 
was widely published, work has been done to examine the use of a low sodium diet for the 
use of forced resting commercial layers (Begin and Johnson, 1976, Whitehead and 
Shannon 1974; Berry and Brake, 1985; Dilworth and Day, 1976; Nesbeth et al., 1976a,b; 
Campos and Baiao, 1979; Naber et al., 1980; Ross and Hernck, 1981). This practice has 
been explored for use as a forced resting procedure, and has been found to be as effective 
as other treatments and is probably more humanely acceptable. Much of the work with no 
added salt or low sodium diets has involved the post treatment effects on egg quality and 
egg production (Begin and Johnson, 1976; Naber et al., 1980). Little has been done to 
make possible the identification of a salt deficiency as a result of feeding a low salt diet as a 
cause of decreased egg production. Analysis of the feed would confirm the omission of 
salt from the diet but a feed sample is often not available. There may be other physiological 
changes occurring at the same time or even earlier than production changes which would 
provide evidence of the sodium deficiency. 

The present study was undertaken to examine some of the physiologic changes 
associated with feeding a low salt diet which might be detectable during the evaluation of a 
flock experiencing a production drop of unknown cause. The mechanism by which a no 
added salt diet causes a cessation of production remains unknown. It is known that long 
term administration of a low salt diet induces regression of the reproductive tract just as do 



32 



33 

other methods of forced resting (Berry and Brake, 1985; Nesbeth, 1976). These 
experiments were conducted to determined whether a hen immediately ceases follicular 
development or whether follicular development continues without ovulation past the 
cessation of egg production. The study also evaluated the effect of removing salt from the 
feed for various times. 



Materials and Methods 

Two experiments were conducted using Hy-Line W36 hens, 60 and 64 weeks of 
age, from different flocks. The hens were individually caged in open-sided houses and 
exposed to a 15 hour light: 9 hour dark photoperiod. Egg production was recorded daily. 
The low salt diet (Table 5-1) was formulated by omitting the added salt from the complete 
diet. 

Experiment 1 

Sixty-hens were placed on a low salt (no added salt) diet. These hens were 
randomly selected and necropsied on days 10, 1 1, 14 and 19 to ascertain the effect of the 
low salt diet on ovarian activity. Ten additional hens were fed a control diet and necropsied 
on day 1 1. The hens were euthanized via cervical dislocation and necropsied. The ovaries 
were carefully examined for evidence of active or regressing follicles. Regressing follicles 
were identified by changes in appearance including color, size and turgidity. On day 11, 
blood samples were collected prior to euthanasia from the low salt diet and the control hens 
utilizing the brachial vein. The sample was kept on ice until spun down within one hour of 
collection and then the serum separated and frozen until analysis. The serum was analyzed 
via flame photometry for sodium and potassium. 



34 

Experiment 2 

Eight treatments were used with 2 replicates of 10 hens each. Each treatment group 
received a low salt diet for a different length of time. The control group received a 
complete diet with added salt for the entire experiment. Seven other groups received the 
salt deficient diet for 5, 6, 7, 8, 9, 10 or 21 days and then switched to a complete diet. 
Feed consumption was determined for various periods of time throughout the experiment. 
Egg weights were measured for all eggs produced during days five through eleven of the 
experiment. Egg specific gravity was determined by suspending eggs in salt solutions with 
specific gravities ranging from 1.060 to 1.0975 in increments of 0.0025. Specific gravity 
of eggs was determined during weeks five, six and seven after initiation of the experiment 
to determine any effects on shell quality. Body weights were determined on the day before 
initiation of the experiment and 30 days later. Hens were examined at 35 days for evidence 
of molting. Hens growing one or more primary feathers were considered as having 
molted. Data from the experiments were analyzed for statistical significance using analysis 
of variance. Treatment means were compared using Duncan's multiple range test (1955). 



Results and Discussion 
Experiment 1 

All 10 hens necropsied after five days on the low salt diet exhibited active follicular 
development on the ovaries. Eight of the 12 necropsied after they had received the no salt 
diet for 10 days had active ovaries while four had evidence of regressing follicles. On day 
1 1, the hens which had received no salt had regressing follicles while the ten control birds 
had active follicular development. On day 14, only one hen out of six that received the no 
salt diet had active follicles. On day 19, both hens examined had regressing follicles. It 
appeared that the largest follicle began regressing first and that the other follicles followed 
in order of size. No new follicular appeared to be developing once regression w 



Las 



35 

initiated. Serum samples from the hens receiving the low salt diet contained a significantly 
higher potassium and a lower sodium level (Table 5-2) when compared to hens receiving 
the control diet. 

Experiment 2 

Egg production declined after six days in all groups receiving the low salt diet 
except those receiving the low salt diet for five days (Figure 5-1). The decrease in 
production of each group mirrored the length of time they received the low sodium diet. 
Hens maintained on a low salt diet for 21 days reached zero production. All hens except 
the group receiving no salt for 21 days returned to production within 14 days after being 
placed on a diet with added salt. 

Feed consumption decreased while the hens were receiving a low salt diet and 
remained lower in those groups for as much as 21 days after they were returned to the 
control diet (Table 5-3). In general, the hens exhibited a greater decrease in FC in 
accordance with the length of time they were fed the low sodium diet. After day 21, feed 
consumption was not significantly different for the control group and hens which had 
received the low salt diet for nine days or less. 

Egg weights were lower by the sixth day in groups receiving the low salt diet 
(Table 5-4). In general, after the seventh day egg weight at was reduced with all groups 
fed the no salt diets. The ten and 21 day groups produced the smallest eggs. 

Specific gravity of eggs were similar from all hens five weeks after initiation of the 
experiment (Table 5-5). During weeks six and seven all hens which had been on low 
sodium diets for nine days produced eggs with higher specific gravity. This increase in 
specific gravity had decreased at 35 days except for hens that received the low salt diet for 
more than nine days. 

At 35 days, only one of the control hens showed evidence of molting (Figure 5-2). 
All hens in the 21 day group appeared to be molting or had recently molted. The level of 



36 

molting in the other low sodium groups generally depended on the length of time they had 
received the diet. The trend observed indicates that the longer a group of hens remains on 
low sodium, the greater percentage of hens that will respond by molting. There were no 
significant differences (p = 0.80) in weight gain among treatments (Table 5-5). 

Data from Experiment 1 indicate that hens placed on a low sodium diet continue to 
develop follicles and o\-ulate for at least five days. It appears that not all hens are affected 
at the same time as the decline of production is gradual in a flock. Not all hens will cease 
laying the same day. Body weight and individual feed intake may contribute to this. Hens 
will continue to develop active follicles until they cease laying. After that, no new follicles 
appear to develop until restoration of the sodium levels in the diet. The largest follicle 
begins to regress first followed by the other follicles in order of diminishing size. Hens 
necropsied just as they were apparently going out of production often had several smaller 
follicles which appeared normal while several larger follicles were becoming atretic. One 
hen was found to have a hard shelled egg in utero and the single largest follicle was just 
beginning to regress while all the smaller follicles still appeared normal. It would seem that 
this was to be the last egg this hen would have laid until returned to a control diet. This 
finding contradicts the findings of Nesbeth et al.. (1976a) who reported a reduction in the 
size of the ovary but no atretic follicles. In that study, however, the ovaries were examined 
in only four hens after 14 days on low salt diet. 

Feed intake was reduced in the hens fed the low salt diet. This agrees with the 
findings in the previous studies. Nesbeth et al. (1976b) reported that this decrease occurs 
within the first 24 hours after the reduction in salt intake. The groups which received the 
low salt diet for a longer time had greater decreases in feed intake. Groups receiving the 
low salt diet for ten days consumed 42.8% less feed than the control group over the same 
ten day period. The decrease in feed consumption continued for up to 28 days after the 
return to an adequate sodium level diet but the difference became less with time. 



37 

Egg production decreased as expected in the hens on low salt diets. However, the 
group which received the low salt diet for only five days did not significantly decrease in 
production. The group receiving the low salt diet for six days had a definite drop 
production but quickly rebounded to the levels of the control group once returned to a 
control diet. The groups receiving the low salt diet for seven, eight, nine and ten days had 
progressively larger declines in production as the length of time on a low sodium diet 
increased. The return to control production levels also took longer for the groups receiving 
low sodium diets for a longer time period. The group receiving the low salt diet for 21 
days reached zero production in 21 days and took the longest time, about 14 days, to return 
to control production levels. Nesbeth et al. ( 1976a) reported hens receiving a low salt diet 
for 23 days returned to normal production levels only seven days after being returned to a 
control diet. Monsi and Enos (1977) reported a return to control production levels over a 
four week period. 

Serum sodium and potassium values decreased in the hens fed low salt diets for 1 1 
days in Experiment 1 (Table 5-2). The increase in potassium would be expected in a 
sodium deficient state as the sum of cationic and anionic components in the blood must 
equal zero to insure electroneutrality of the blood. Cohen et al. (1974) found differences in 
plasma sodium and potassium when hens were fed varying levels of these nutrients. The 
differences in sodium were not significant (p < 0.05) but the lowest sodium level fed was 
0.1% for 7 to 8 days. When no added salt is used in a corn-soy based diet, a level of 
approximately 0.02% salt is fairly typical. 

Egg weights were significantly lower in the low salt groups on day 6 and continued 
to decline in the groups as they remained on the low sodium diet (Table 5-5). On day 11, 
the 21-day and 10 day groups, the groups receiving low sodium for the longest times, 
produced the lightest eggs. Previous work has also reported a decrease in EW (Begin and 
Johnson, 1976; Whitehead and Shannon, 1974). 



38 

Specific gravity of eggs produced by the hens in Experiment 2 was checked to 
confirm that no loss of shell quality occurred due to treatment. At week five there was no 
difference between the treatment and control groups (Table 5-5). At weeks six and seven, 
there was a significant improvement in specific gravity of eggs produced by most of the 
treatment groups. This was interesting as most of the hens had received the low salt diet 
for ten or less days. This was a much shorter time period than used in any of the other 
resting (molting procedures). 

The percentage of hens showing evidence of molting at 35 days was related to the 
time they received the low salt diet (Figure 5-2). The control group had less than 4% 
molted birds while all the hens receiving low salt for twenty-one days either had molted or 
were molting. In the other low salt groups molting increased as the length of time on the 
low sodium diet increased. 

These decreases in production, egg weight and feed consumption in a flock six to 
ten days after being fed a new feed would indicate the need for necropsy, blood sampling 
for electrolyte analysis, and feed analysis. These simple procedures could quickly confirm 
a salt deficient situation which could be remedied by adding salt to the feed. If the feed is 
changed, there should be a return to normal production within one to two weeks with no 
loss of egg quality depending on how long the salt deficient diet was fed. 



TABLE 5- 1 . Composition of diets 



39 



Ingredient 


Control 




Low Salt 









% 






Corn 

Soybean Meal (48%) 


73.57 
15.83 




73.95 
15.83 




Limestone 


8.85 




8.85 




Dicalcium Phosphate 1 
Microingredients 2 


0.79 
0.50 




0.79 
0.50 




Salt 
DL-methionine 


0.38 
0.08 




0.00 
0.08 




Nutrient 




Calculated Analysis 






Protein % 
Calcium % 


14.20 
3.60 




14.24 
3.60 




Phosphorus % 


0.45 




0.45 




Sodium % 

MetabolizableEnergy 

(kcal/kg) 


0.17 
2879 




0.02 
2892 





•Dicalcium phosphate (18.5% phosphorus and 21% calcium) 
2 Provides per kg of diet: 6600 IU Vit A; 2200 ICU Vit D 3 ; 2.2 mg 
menadione dimethylprimidinol bisulfite; 4.4 mg riboflavin; 39.6 mg niacin; 13 mg 
pantothenic acid; 500 mg choline; 0.02 mg vit B 12 ; 125 mg ethoxyquin; 60 mg Mn; 50 mg 
Fe; 60 mg Cu; 0.2 mg Co; 1.1 mg I; 35 mg Zn, selenium, 0.1 mg. 



40 



TABLE 5-2. Serum sodium and potassium from hens 1 receiving a control or low salt diet 
for 1 1 days (Experiment 1) 



Pj£j Sodium Potassium 

(mg/dl) 
Control 140.3 ± 2.6 a 4.5 ± 0.2 a 

Low Salt 129.9 ± 49 b 5.7 ± 0.9b 



a,b Means with different letters within columns are significantly 

different (P < 0.05) 
'Samples analyzed from 10 hens per diet. 



41 



TABLE 5-3. Feed consumption of hens when a low salt diet was fed for the indicated 
periods of time 



Days on Low Feed Intake 1 

Salt 



1-21 Days 22-35 Davs 36-49 Davs 



107.0 + 4.83(10) 109.9 ± 3.43(11) 105.7 ± 5.0 s 98.5 ± 4.9 

5 83.8 ± 1.8b(5) 96.3 ± 14.4 b (16) 104.6 ± 0.3 a 100. 1 ± 2.1 

6 72.8±1.4 C (6) 83.9 + 2.2^(15) 100.5 + 2.5 ab 99.8 ± 1.7 

7 71.1 ± 1.3 C (7) 89.0 ± 2.1 bc (14) 108.2 ± 0.7 a 103.0 + 3.4 

8 69.9±0.1 c (8) 81.9 ±5.5^(13) 100.7 ± 6.53b 99.3+1.9 

9 69.4 + 47 c (9) 67.8 + 15.(^(1 2) 100.7 + 0.8 a b 97.9 ± 1.0 

10 61.2 + 2.4 d (10) 66.3 + 0.7 c (ll) 96.7±4.1 b 97.5 ± 6.8 
21 * * 96.5+ 1.5 b 100.9 ±4.7 



! Feed intake during this period was broken into two periods which totaled the 21 days as 

indicated in parenthesis. These differ for each treatment as feed intake was measured 

during the time the low salt diet was fed. 

*Feed intake was not measured during this time period. 

3-dMeans with different letters within columns are significant different (P < 0.05). 



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43 



TABLE 5-5. Specific gravity of eggs from hens during the fifth, sixth, or seventh week 
after receiving a control or low salt diet for varying lengths of time and weight gain from 
day one to day thirty 



Days of Low 




Specific Gravity A 




Body Weight 


Salt 








Gain (g) 




Week 5 


Week 6 


Week 7 







839+46 


788±56 ab 


800+33 a 


18.6 


5 


847±64 


803±44 ab 


822±37 ab 


34.7 


6 


836±67 


805±72 abc 


818±67 ab 


16.1 


7 


843±41 


823±47 bc 


828±46 ab 


24.1 


8 


829+60 


804±46 abc 


814±57 ab 


22.1 


9 


827±52 


836±42 c 


838±39 b 


3.9 


10 


829±64 


826+39^ 


827±34 ab 


3.2 


21 


833+38 


813±59 abc 


825±39 ab 


1.7 



A x±SEM (Coded 1.0XXX) 

a " c Means with different letters within columns are significantly different (P<0.05) 



44 




18 21 26 31 

DAYS ON EXPERIMENT 



41 



Figure 5-1. Egg production of laying hens for forty-one days after being fed a low salt diet 
for different lengths of time. 



45 




Figure 5-2. Percent of hens molting when fed a low salt diet for 0, 5, 6, 7,8,9, or 21 
days. 









CHAPTER 6 
DETERMINATION OF CYCLICITY OF PLASMA SODIUM 



Introduction 

Some minerals in plasma, such as calcium and phosphorus, have been shown to 
vary- over a cycle in relation to oviposition in the laying hen (Mongin and Sauveur, 1979, 
Miller et al., 1977). This is due to changes in the substances being secreted for deposition 
during egg formation. Preliminary work in Europe showed evidence of a cycle for sodium 
concentration, hematocrit and plasma protein during egg laying (Rzasa et al., 1982). This 
study was undertaken to reexamine evidence for sodium cyclicity and to more accurately 
determine the nature of such a cycle. 

Materials and Methods 

Sixteen HyLine W-36 hens were selected on the basis of consistent production. 
These hens were individually caged and provided free access to water and a complete layer 
feed. Appropriate size (rat size) vascular access devices (VAD) were implanted in 16 
laying hens. The VAD was to allow repeated blood sampling from a single hen without the 
neccessity for repeated venipuncture. The VADs had a port which was placed on the 
center of the back for easy access. Anesthesia was induced and maintained with isoflurane 
in 100% oxygen delivered via direct flow. The birds were placed in left lateral 
recumbency and feathers plucked from an area including the region of the featherless 



46 



47 

tract over the right jugular vein and extending across the center of the back. Skin was 
aseptically prepared and draped. A 4 cm longitudinal skin incision was made 2 cm to the 
right of midline just caudal to the thoracocervical vertebral junction. The skin was 
dissected free from the underlying musculature to allow for subcutaneous placement of the 
port of the VAD. The port was centered over the thoracic vertebrae and sutured to the 
adjacent epaxial musculature. Following port placement, a 2 cm skin incision was made 
over the right jugular and the vessel was dissected free from the surrounding tissue via 
blunt dissection. The catheter was tunneled subcutaneously from its point of origin on the 
back to exit the incision over the jugular vein. A 2-3 cm segment of the jugular vein was 
exteriorized and the proximal extent of the exteriorized vein was ligated. A temporary 
occluding loop of suture was placed at the distal extent of the exteriorized segment of the 
jugular vein. A small incision was made into the vessel between the ligatures and the 
heparinized saline loaded VAD was introduced into the lumen and advanced into the right 
atria. The occluding loop of suture was tied to secure the VAD into the vein, and the VAD 
was further secured with 1 or 2 ligatures to the subcutaneous tissue. The skin was closed 
using nonabsorbable suture in a simple interrupted suture pattern. The hens were then 
allowed to recover, which generally took five minutes, and returned to the cage. Hens 
were maintained for 2 weeks prior to initiation of sampling. 

On sampling day, hens were observed for oviposition and sampled within five 
minutes after oviposition and at two, four , six and eight hours after oviposition. The 
blood was then placed in blood collection tube, centnfuged and the serum removed. Serum 
was then analyzed via flame photometry for sodium and potassium. 

Results and Discussion 

It was hypothesized that if plasma sodium did indeed cycle in relation to 
oviposition, the cycle may be due to the secretion of sodium into the albumen. The whole 



48 

egg contains 73.7 mg of sodium (Cotterill et al, 1977). The albumen contains 60.9 mg or 
83% of the sodium which would have to be withdrawn from the blood at the time of 
albumen secretion which potentially would lead to a change in plasma sodium. Thus, 
sampling was done during the times before, during and just after predicted albumen 
secretion would be occurring based on the previous oviposition. Little sodium is contained 
in the shell so it was elected to concentrate sampling efforts where a change was most likely 
to be found. Rzasa et al. ( 1982) found changes associated with oviposition in laying hens 
versus control hens in plasma sodium, hematocrit and total protein. Samples in their 
experiment were drawn 90 and 30 minutes prior to ovulation and 30 and 90 minutes after 
ovulation. They found that the sodium was lowest 90 minutes prior to oviposition, 
peaking at oviposition and declining later (Table 6-1). They found no significant changes 
in plasma potassium. 

There was some indication of sodium varying across time (P=0.09) but not 
significandy (Table 6-1). However, the sodium decreased progressively over time, into the 
time of shell secretion, which did not agree with the hypothesis. Phosphorus cycles over 
time, which agrees with previous research. In contrast to results in chapter 5, potassium 
does not seem to increase as plasma sodium is reduced. However, in this experiment hens 
were fed a normal layer diet while the hens in chapter 5 were placed on a sodium deficient 
diet which may account for the difference. Chloride is found to significantly decrease over 
time following oviposition. This result may be in error due to the small sample size 
evaluated for chloride at the 8 hour point ( 4 samples) and as the value is outside the limits 
consistent with life. There was a value outside of two standard deviations which may have 
skewed the results. All other blood constituents examined did not vary significandy over 
time. 



49 



TABLE 6-1. Hematocrit and plasma protein, sodium and potassium levels during 
oviposition in the domestic hen (means±SE) (Rsaza et al., 1982) 



Time Hematocrit Protein (g/1) Sodium Potassium 
(mmol/1) (mmol/1) 



90 min before 0,28 ±0,014 46,35+1,06 149,2 ±2,27 5,47 ±0,11 

oviposition 

30 min before 0,27 ±0,013* 45,00 ±1,82 153,4 ±2,57 5,49 ±0,20 

oviposition 

During 0,27 ±0,013* 43,50 ±1,74* 156,2 ±2,23* 5,85 ±0,49 

oviposition 

30 min after 0,25 ±0,011** 42,46 ±1,55* 154,9 ±2,59 5,53 ±0,28 

oviposition 

90 min after 0,24 ±0,010** 41,84 ±1,85* 152,4 ±2,49 5,00 ±0,22 
oviposition 



* ** 



Significance of differences from controls *P<0,05; **P<0,01. 
Each value represents the mean from seven hens. 



50 



TABLE 6-2. Various plasma constituents from laying hens over time from oviposition to 
eight hours later 



Plasma 
Consituent 




Oviposition 


5 
Minutes 


2hrs 


4hrs 


6hrs 


8hrs 


P value 


Sodium 
(meq/1) 


Avg 


156.00 


155.11 


153.82 


148.09 


147.80 


147.00 


0.09 




SEM 


1.30 


1.87 


1.40 


3.99 


3.11 


7.49 




Cholesterol 
(mg/dl) 


Avg 


151.23 


153.78 


150.64 


149.00 


144.27 


126.75 


0.79 




SEM 


8.27 


12.50 


10.25 


10.65 


8.74 


13.54 




Phosphorous, 


















inorganic 
(mg/dl) 


Avg 


5.79 


6.08 


5.28 


5.15 


5.01 


4.28 


0.03 




SEM 


0.34 


0.30 


0.35 


0.24 


0.21 


0.57 




Calcium 
(mg/dl) 


Avg 


25.08 


25.59 


25.93 


26.32 


25.50 


22.43 


0.60 




SEM 


1.27 


0.97 


1.17 


0.67 


0.85 


2.93 





Potassium 
(meq/1) 


Avg 


4.21 


4.19 


4.09 


4.21 


4.33 


3.90 


0.90 




SEM 


0.23 


0.25 


0.16 


0.15 


0.15 


0.39 




Chloride 
(meq/1) 


Avg 


1 17.00 


116.44 


115.00 


113.89 


109.36 


85.50 


<.0001 




SEM 


1.62 


1.51 


1.66 


2.18 


4.43 


12.16 




Total Protein 
(g/dl) 


Avg 


5.52 


5.58 


5.29 


5.33 


5.22 


5.03 


0.61 


A IL-Qlir>«> 


SEM 


0.18 


0.21 


0.21 


0.18 


0.20 


0.30 





Phosphatase A vg 544.23 481.44 622.08 507.00 551.09 573.25 0.69 
SEM 69.32 43.36 72.42 45.58 42.94 116.34 




CHAPTER 7 

THE ABILITY OF HENS TO REGULATE CHLORIDE INTAKE WHEN 

OFFERED SODIUM FROM SODIUM CHLORIDE AND SODIUM 

BICARBONATE 



Introduction 



Researchers in the past have examined the laying hen's ability to regulate intake of 
various nutrients when offered a choice. Graham (1934) examined the capability of laying 
hens to balance their own diets by offering a selection of ingredients. Others have 
compared the hen's ability to regulate intake of specific nutrients when offered a choice of 
diets with varying levels of that nutrient. Holcombe et al. (1976a) found that hens could 
distinguish and choose a diet with sufficient protein over a low protein diet incapable of 
supporting egg production. Holcombe et al. (1976b) also found the hen clearly able to 
regulate phosphorus or calcium intake when offered various levels of phosphorus at 
constant and varying levels of calcium. 

The ability of hens to regulate sodium intake has not been thoroughly investigated. 
In an unpublished study it was reported that hens were unable to regulate sodium intake 
(Nesbeth and Douglas, 1976). Previous studies have often utilized sodium bicarbonate as 
a sodium source when examining the effects of excess sodium (Davison and Wideman, 
1992). Some have suggested sodium bicarbonate to be almost essential for improvement 
of egg shell quality (Garlich 1979). 



51 



52 
Materials and Methods 

An experiment was conducted using HyLine W-36 hens, 61 weeks old, to 
determine their ability to regulate sodium intake when offered a choice of two diets 
containing different sodium sources. A corn-soybean basal diet that had been previously 
fed was used (Table 7-1). Sodium chloride was the sodium source in the control diet and 
sodium bicarbonate was used in the experimental diet . Hens were maintained in individual 
cages in seven replicates of five hens each. Each hen was provided with two identical feed 
cups as described by Roland et at. (1971). The control group was offered the control diet 
in both cups, and the experimental group received the control diet in one cup and the 
experimental diet in the other. The experiment was conducted for four weeks. The 
position of the diets was altered so that half the pens received one diet on the right and the 
other half received that diet on the left. Feed consumption was measured every five days. 

Egg production was recorded daily. Egg and shell weight measured once a week. 
Eggs were weighed, broken out, shells washed and allowed to air dry for seven days prior 
to measuring shell weight. Data was subjected to the student's t test. 

Results and Discussion 

Egg production and EW were not significantly different between the two groups 
(Table 7-2). Shell weights were not significantly different (p=0.072) although the 
bicarbonate group consistently had a numerically higher value. The percentage of S W to 
EW was significantly different with the bicarbonate group having heavier shell 
percentages. 

During the first week the bicarbonate group exhibited a preference to eat from the 
right cup. This preference was not evident by the second week as there was no significant 
difference in FC from the right cup versus left cup in either group. However, when 



53 

examining sodium intake, the bicarbonate group had higher sodium intake than the control 
group. The experimental group had higher sodium intake than hens receiving the control 
feed. The control group had significantly higher chloride intake than the bicarbonate 
group. Again this may have resulted from equal intakes of the two feeds which varied in 
chloride content. 

The EW, SW, EP and FC were not significantly altered by the offering of the two 
diets. However, the percentage of SW to EW was significantly improved by offering the 
hens a choice of diets with bicarbonate or NaCl. This agrees with previous reports that 
replacing a portion of NaCl with sodium bicarbonate in the diet will improve egg shell 
quality. The chloride intake of the two groups were significantly different but without 
detrimental effects on production. It does not appear that the hens were able to adjust their 
consumption of the two diets in order to balance chloride. 



54 



TABLE 7- 1 . Composition of diets 



Ingredient 


Control 




Bicarbonate 






% 




Corn 


67.12 




67.07 


Soybean Meal (48%) 


21.51 




21.51 


Ground Limestone 


8.69 




8.69 


Dicalcium Phosphate 3 


1.56 




1.56 


Salt 


0.39 




0.00 


Microingredients b 


0.60 




0.60 


DL-Methionine 


0.14 




0.14 


Sodium Bicarbonate 


0.00 




0.43 


Nutrient 


Protein 


15.67 




15.67 


Calcium 


3.72 




3.72 


Phosphorus 


0.61 




0.61 


Sodium 


0.19 




0.14 


Metabolizable Energy (kcal/kg) 


2879 




2892 



a Dicalcium phosphate ( 18.5% P, 21% Ca) 

^Supplied per kilogram of diet vitamin A, 6,600 IU; vitamin D 3 , 2,000 ICU- menadione 
dimethylpynmidinol bisulfite, 2.2 mg; riboflavin, 4.14 mg; pantothenic acid 13 2 mg- 
niacin, 39.6 mg; vitamin Bi 2 , 0.022 mg; choline chloride, 499.4 mg; ethoxyquin 125 
mg; manganese, 60 mg; iron, 50 mg; copper, 6 mg; iodine, 1.1 mg; zinc, 35 mg; 
selenium, O.lmg. 



55 



TABLE 7-2. Performance of hens offered a choice of diets with sodium chloride or 
sodium bicarbonate 





Control 


Bicarbonate 


P value 


Egg Production (%) 


86.6 


87.1 


0.7891 


Egg Weight (g) 


59.60 


59.63 


0.9556 


Shell Weight (g) 


5.61 


5.74 


0.0719 


Shell Percent (%) 


9.41 


9.64 


0.0174 


Feed Intake(g/h/d) 


100.6 


104.4 


0.1461 


Sodium Intake (mg/d) 


150 


158 


0.0021 


Chloride Intake (mg/d) 


280.8 


155.0 


0.0001 









CHAPTER 8 
SODIUM REQUIREMENT FOR BROILER BREEDER HENS 

Introduction 

Little research has been directed at the sodium requirement of the broiler breeder. 
Most work has been in chicks or laying hens and there is not consistent agreement in the 
literature regarding the sodium requirement of these categories of birds. The National 
Research Council (1977) suggested that feed for broiler breeder hens should contain 0.20% 
sodium . Damron et al. (1983) reported that increasing supplemental sodium chloride 
levels above 0. 12% did not improve performance of broiler breeders. The diet containing 
0.12 % supplemental NaCl supplied 154 mg Na per hen per day. Therefore, the NRC 
( 1984 and 1994) lowered their suggested requirement to 150 mg Na per hen per day. This 
suggested level is the lowest level that was fed by Damron et al. (1983). This study was 
conducted to further evaluate the Na requirement of the broiler breeder hen. 



Materials and Methods 



Two experiments were conducted with Arbor Acre 1 hens. The experiments began 
when the hens were 57 and 55 weeks of age in Experiment 1 and 2, respectively. Com- 



1 Arbor Acres Inc., Gastonbury, CT 06033. 



56 



57 

soybean meal diets were used (Table 8-1). The basal diet was calculated (NRC, 1984) to 
contain 0.0227c Na and by chemical analysis 2 contained 0.021%. The calculated value 
was used in the discussion of the results. Five experimental diets were used in experiment 
1, which contained sodium chloride to furnish daily intakes of 35, 65, 95, 125, and 150 
mg of Na. In Experiment 2, the diet furnishing 150 mg per day was replaced with a diet to 
furnish a daily intake of 180 mg Na per day. Chemical analysis of the water (City of 
Gainesville, Florida) indicated that it contained 12 ppm. Eight replicates of eight hens each 
were fed each experimental diet. Hens were housed in floor pens having 2.3 1 m 2 floor 
space, an automatic waterer, a hanging tube feeder, and four individual nests. Wood 
shavings were used as litter and nesting material. Hens were fed at 1000 h each day and 
given a daily feed allowance of 157 and 158.4 g per hen per d in Experiments 1 and 2, 
respectively. Each experiment was conducted for 12 wk. 

Egg production was recorded daily by pen. Egg weight and specific gravity were 
measured on 1 d production/wk in Experiment 1. Specific gravity was not measured in 
Experiment 2. Egg mass was calculated by multiplying EP by EW. Specific gravity was 
measured by the procedure of Voisey and Hamilton (1977), taking measurements in 
increments of .0025. Body weights were obtained at the beginning and end of Experiment 
1, and only at the end of Experiment 2. 

On day 28, blood samples were obtained from the brachial vein of ten hens 
receiving each diet. The hens were selected at random with at least one hen selected from 
each pen on each diet. The samples were kept on ice until centrifuged within one h of 
collection and the serum was separated. Serum was analyzed via flame photometry 3 for 
sodium and potassium concentration. 



2 Woodson-Tennant Laboratories, Inc. P.O. Box 2135, Memphis, TN 38101. 
3 Flame Photometry Model No. 943, Instrumental Laboratories, Lexington, MA 02173. 



58 

One-way analysis of variance (SAS Institute, 1982) was used to measure weekly 
treatment effects. Pen averages were used for measurement of EP, EW, EM, specific 
gravity and BWC. Plasma sodium and potassium values for individual hens were used for 
analyses. 

The residual mean square was used as the error term. The requirement of sodium 
for EP and EM was determined by the segmented broken-line model (Noll and Waibel, 
1989). The data for six to nine wk were used in Experiment 1, and six to 12 vvk in 
Experiment 2. Differences between treatment means (P<0.05) were determined by 
Duncan's Multiple Range test (1955). 

Results and Discussion 

Egg production was significantly reduced during the fourth wk in Experiment 1 

when hens received the basal diet with no added sodium (Table 8-2). This finding agrees 

with a previous report (Sloan and Harms, 1992) that hens would produce at a maximum 

rate for 3 wk when their diet contained no supplemental sodium. Egg production was 

numerically reduced in the fifth vvk in Experiment 2 and significantly reduced during the 

seventh wk when the hens received a daily intake of 35 mg Na/h/d when compared to hens 

receiving the higher levels of Na (Table 8-3). Egg production also decreased at 7 wk in 

Experiment 2 when the hens had a daily intake of 65 mg Na/h/d or less (Table 8-3). There 

was no decline in EP with an intake of 95 mg Na/h/d. Hens receiving the basal diet did not 

cease EP during the 12 wk experiment. This also agrees with the report of Sloan and 

Harms (1992), however, it is different than the response of commercial layers as reported 

by Nesbeth et al. ( 1976). Sloan and Harms ( 1992) suggested that the different response of 

commercial layers and broiler breeders is due to a greater feed intake of the broiler breeders 

and recycling of sodium through consumption of litter resulting in a greater intake of 

sodium. 



59 

Egg weight for hens fed the basal diet in Experiment 1 was reduced during the first 
wk (Table 8-2). Eggs remained significantly smaller wk 5 through wk 9 when compared 
with other treatments. In Experiment 2, EW from hens fed the basal diet was not reduced 
until the eighth and ninth wk (Table 8-3). The reduction in EW in Experiment 1 is similar 
to the findings of Sloan and Harms (1992), but the findings in Experiment 2 differed from 
the results in Experiment 1, and with those of Sloan and Harms ( 1992). These differences 
may be due to changes in EW and EM in the different experiments. The eggs weighed in 
excess of 70 g in the studies by Sloan and Harms (1992), as compared with slightly less 
than 70 g in Experiment 1 and approximately 62 g in the second experiment at initiation of 
each study. 

Egg mass was significantly reduced in week 4 (Table 8-2, 8-3) when the hens 
received the basal diet. Egg mass was significantly reduced in Experiment 1 during week 6 
when hens had a daily sodium intake of 65 mg/h. When hens had an intake of 65 mg 
Na/h/d in Experiment 2, EM was not reduced until week 7. 

In Experiment 1 , specific gravity of eggs was not significantly different for the eggs 
from hens fed the basal diet than for hens fed diets containing supplemental sodium (Table 
8-2). This agreed with the findings of Sloan and Harms (1992). Therefore, specific 
gravity was not measured in Experiment 2. 

Plasma sodium was significantly lowered when hens were fed the basal diet (Table 
8-4). The decrease in plasma sodium was accompanied by an increase in plasma 
potassium. The decreased sodium and increased potassium which occurred when the low- 
sodium diet was fed agrees with findings for commercial layers (Kuchinski and Harms, 
1994). However, plasma levels of both sodium and potassium were lower in their study 
with commercial layers than in the broiler breeder hens. Increasing the sodium intake to 65 
mg/d resulted in increased plasma sodium and reduced plasma potassium. A further 
increase to 95 mg/d resulted in another increase in sodium and a further reduction of 
potassium. Increasing the sodium intake above 95 mg/d did not affect plasma sodium and 



60 

potassium. Plasma sodium and potassium for hens maintained in cages and fed a sodium- 
deficient diet resulted in similar changes to those observed in Experiment 1 (unpublished 
data). The sodium and potassium values for broiler breeder hens were similar to those 
observed in commercial layers. 

Weight gain (Table 8-2) and BW (Table 8-3) were significantly reduced when the 
diet supplied 65 mg Na/d. There was a further significant decrease in weight gain when the 
diet supplied 35 mg Na/h/d. Weight gain or BW did not differ significantly for the groups 
receiving the three highest levels of sodium. 

When EP was regressed on sodium intake (Table 8-5) the sodium requirement was 
1 13.8 and 96.0 mg/h/d in Experiments 1 and 2, respectively. When EM was regressed on 
sodium intake (Table 8-5) the sodium requirement was 105.0 and 100.0 mg/h/d in 
Experiments 1 and 2, respectively. Egg production was higher in Experiment 1 than in 
Experiment 2. This may account for the difference in requirement between the two 
experiments. Also this may indicate that the requirement would be higher at peak 
production. The requirements in the present study are lower than suggested by NRC 
(1984, 1994). However, their recommendation was based on a report by Damron et al. 
( 1983) who indicated no more than 154 mg Na/h/d was required. 



61 



TABLE 8- 1 . Composition of diets 





Basal 




High 


Sodium 






Experiment 1 


Experiment 2 


Ingredient 












(%) 






Ground Corn 


74.34 


74.15 




75.31 


Soybean Meal (47% CP) 


18.30 


18.30 




16.80 


Limestone 


6.30 


6.30 




6.51 


Dicalcium phosphate 1 


0.60 


0.60 




0.68 


Microingredients 2 


0.46 


0.46 




0.46 


Salt 




0.19 




0.23 


Calculated analysis (%) 










Calcium 


2.61 


2.61 




2.69 


Phosphorus (total) 


0.43 


0.43 




0.44 


Sodium 


0.02 


0.10 




0.11 


Protein 


14.11 


14.11 




14.22 


Methionine 


0.25 


0.25 




0.26 


Lysine 


0.75 


0.75 




0.71 


Tryptophan 


0.16 


0.16 




0.18 


ME (Kcal/kg) 


2936 


2930 




2933 



1 Dicalcium phosphate (18.5% P, 21% Ca) 

2 Supplied per kilogram of diet: vitamin A, 6,600 IU; vitamin D 3 , 2,000 ICU; menadione 
dimethylpyrimidinol bisulfite, 2.2 mg; riboflavin, 4.14 mg; pantothenic acid, 13.2 mg; 
niacin, 39.6 mg; vitamin B 12 , 0.022 mg; choline chloride, 499.4 mg; ethoxyquin, 125 
mg; manganese, 60 mg; iron, 50 mg; copper, 6 mg; iodine, 1.1 mg; zinc, 35 mg'; 
selenium, 0.1 mg. 



62 



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64 



TABLE 8-4. Plasma sodium and potassium content from broiler breeder hens fed various 
levels of dietary sodium (Experiment 1) 



Sodium intake Sodium Potassium 



mg/hen/day (mg/dl) 

35 141.3 b 7.05 a 

65 lSO.O 313 6.89 a 

95 155. la 636 ab 

1-5 156. 1^ 5. 76 b 

150 155.3 a 5.6 l b 

Pooled SEM 5.4 0.71 



ab Means with no common superscript within a column are significantly different. 
(P<0.05) 



65 



TABLE 8-5. Regression parameters for egg production and egg mass regressed on sodium 
intake (Experiment 1) 









Parameters 








Intercept 


Slope 


Break point 


R2 


Probability 








Experiment 1 






Egg production 


15.7 


0.42 


113 


0.72 


.0001 


Egg mass 


9.4 


0.35 


105 
Experiment 2 


0.58 


.0001 


Egg production 


24.6 


0.36 


96 


0.65 


.0001 


Egg mass 


17.0 


0.22 


100 


0.46 


.0001 



CHAPTER 9 
SUMMARY AND CONCLUSIONS 



There is little agreement in the literature on the requirement for sodium or NaCl in 
poultry diets. Additionally, the accidental discovery of potential beneficial uses of low salt 
diets in commercial laying hens has led to various research projects exploring aspects such 
as a more humane method of resting hens. The effect of the low salt diet was attributed 
specifically to the sodium level. Therefore, six series of experiments were conducted to 
further evaluate sodium nutrition in the laying hen. 

The first study consisted of 2 experiments conducted to evaluate the effects of 
removing selected ingredients from a commercial layer diet. In Experiment 1, hens were 
fed four diets: 1 A) a complete diet for hens near the end of the first production cycle; IB) a 
diet containing corn, calcium (4.5%), microingredients, and salt; 1C) diet IB without 
microingredients; or ID) diet IB without microingredients or salt. In Experiment 2, hens 
were fed five diets: 2A) a complete diet for hens less than six weeks to market; 2B) a diet 
of corn, calcium (4.5%), dicalcium phosphate (P), microingredients, and salt; 2C) diet 2B 
without P; 2D) a diet of corn, calcium (6%), P, microingredients, and salt; or 2E) diet 2D 
without P. Feed intake was significantly reduced within 2 d when hens were fed the 
reduced nutrient diets. Egg production was not significantly reduced in treatment groups 
until day 6 after which production decreased rapidly. Egg weight decreased after day 3. 
All eggs produced by hens on the reduced nutrient diets had adequate shell quality required 



66 



67 

for marketing. After 7 d, hens on the reduced nutrient diets had evidence of follicular 
regression. Utilization of reduced nutrient feeding prior to marketing laying hens would 
result in feed cost reduction and continued production of salable eggs. 

Two experiments were conducted in the second study with 36 week old Hy-Line 
W36 hens to determine their sodium requirement A corn-soybean basal diet was used 
which contained 0.056% sodium. Hens in Experiment 1 were maintained in individual 
cages and fed diets containing sodium levels of 0.056, 0.078, 0. 100, 0. 122, 0. 144, 0. 166, 
0.188 and 0.210%. The levels of 0.188 and 0.210 were not fed in Experiment 2. 
Supplemental sodium was provided by NaCl. The city water contained 9 ppm Na. The 
first 2 wk were considered as a depletion period with wk 3-8 and 3-6 used to measure 
treatment effects in Experiments 1 and 2, respectively. 

Reducing the daily Na intake below 114 and 110 mg in Experiment 1 and 2, 
respectively resulted in a significant decrease in egg production during the second week. 
As the level of sodium decreased, EW, FI, and BW decreased. Broken line regression of 
sodium intake on EC in Experiment 1 and egg production in Experiment 2 indicated a daily 
requirement of 1 13 mg/hen/d and 99 mg/hen/d, respectively. 

Much research has studied the use of low salt diets to force rest hens, but little 
focuses on the accidental omission of salt from a commercial laying hen diet. Therefore, in 
the third study, 60 hens were fed a low salt diet (0.02% Na) to investigate the effects on 
ovarian activity. Hens were necropsied on predetermined days and the ovaries carefully 
examined. Follicular development was unaffected for at least 5 d from the imtiation of the 
low salt diet. The follicles of the hens on the low salt diet then underwent regression, 
beginning with the largest follicle and continuing to progressively smaller follicles. Serum 
sodium levels were significantly lower and potassium higher for hens receiving the low salt 
diet for 1 1 d compared to hens receiving a control diet. Egg production, FC, and EW 
decreased in hens receiving the low salt diet for 6 or more days. The longer the hens 



68 

received the low salt diet, the greater the decrease in these parameters. The percentage of 
hens that molted was significantly higher in the low salt groups; the longer the hens 
received this diet, the more significant the molting they experienced. 

A fourth study was conducted to look for evidence of changes in plasma sodium 
associated with oviposition and EP. Sixteen HyLine W-36 hens selected on the basis of 
consistent production were surgically implanted with rat-size vascular access devices to 
allow repeated blood sampling without repeated veimpuncture. Blood samples were taken 
from the hens within 5 minutes of oviposition, and at 2, 4, 6, and 8 hours after 
oviposition. The serum was analyzed for various substances including sodium and 
potassium. Calcium ,potassium, total protein, alkaline phosphatase, and cholesterol 
showed no change over time. Phosphorus and chloride significantly decreased several 
hours after oviposition. Sodium decreased over time but only approached significance 
(P=09). Other blood constituents measured were not affected. 

Researchers in the past have found hens capable of regulating intake of various 
nutrients such as protein and phosphorus when offered a choice of diets with varying 
levels. The ability of hens to regulate sodium has not been thoroughly investigated. 
Researchers have utilized sodium bicarbonate in the diet as a sodium source often to 
examine the effects of excess chloride or in an effort to improv e egg shell quality. Seventv 
61 -week old HyLine W-36 hens were fed a choice of two diets containing two sodium 
sources. A corn-soybean meal basal diet was used with the control diet having NaCl as the 
sodium source and in the experimental diet sodium bicarbonate was used. Each group was 
offered feed in two identical feed cups. The control group was offered the control diet in 
both cups while the experimental group received the control diet in one cup and the 
experimental diet in the other. Egg weights, SW, EP and FC were not significantly altered 
by consumption of either of the two diets. Percent shell was significantly improved by 
consumption of the sodium bicarbonate diet. The sodium and chloride intake of the 2 



69 



groups was significantly different but both groups met their dietary requirements. It does 
not appear that the hens were able to adjust chloride intake. 

Two experiments were conducted with Arbor Acres broiler breeder hens to 
determine their sodium requirement. Sodium chloride was added to a corn-soybean meal 
diet to furnish daily intakes of 35, 65, 95, 125 and 150 mg Na/h in Experiment 1. The 150 
mg level was replaced with 180 mg in Experiment 2. Egg production was significantly 
reduced during week 4, when the hens had an intake of 35 mg Na/d. Egg production was 
reduced by week 7 when the diet furnished 65 mg Na/d. Plasma sodium was reduced and 
plasma potassium increased when the intake was 35 or 65 mg Na/d. Performance data 
from 6 to 9 and 9 to 12 weeks were used in Experiments 1 and 2, respectively, to 
determine the daily sodium requirement. The daily requirement for maximum production 
was 1 13.8 and 96 mg Na/d and the requirement for egg mass was 105 and 100 mg Na/d in 
Experiments 1 and 2 respectively. The response of the broiler breeders to a sodium 
deficiency did not differ from commercial layers except for lack of cessation of EP nor did 
the requirement differ greatly. 



70 



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BIOGRAPHICAL SKETCH 

The author, Kristine K. Kuchinski Broome, was born February 25, 1965, in 
Parma, OH and grew up in Jacksonville, FL. She received her AB from Wesleyan 
College, Macon, GA, majoring in biology. She then received her Doctor of Veterinary 
Medicine from the University of Florida in 1991. Kristine then began work toward a 
Master of Science at the University of Florida under the guidance of Dr. Robert H. Harms. 
After taking a two year hiatus from graduate studies to pursue work on ratites, she returned 
to the University of Florida to pursue the degree of Doctor of Philosophy. 

Kristine is currently conducting research to obtain a Doctor of Philosophy degree 
with emphasis on poultry nutrition. After completing her graduate studies, Kristine plans 
to apply her knowledge by working in the nutrition or veterinary field. 



74 



I certify that I have read this study and that in my opinion it conforms to acceptable 
standards of scholarly presentation and is fully adequate, in scope and quality, as a 
dissertation for the degree of Doctor of Philosophy. 

Robert H. Harms, Chair 
Graduate Research Professor of Dairy 
and Poultry Sciences 

I certify that I have read this study and that in my opinion it conforms to acceptable 
standards of scholarly presentation and is fully adequate, in scope and quality, as a 
dissertation for the degree of Doctor of Philosophy. 




Don R. Sloan 
Associate Professor of Dairy and Poultry 
Sciences 

I certify that I have read this study and that in my opinion it conforms to acceptable 
standards of scholarly presentation and is fully adequate, in scope and quality, as a 
dissertation for the degree of Doctor of Philosophy. 



gjg^g £. TZ-^lL^ 



Henry R. Wilson 

Professorof Dairy and Poultry Sciences 

I certify that I have read this study and that in my opinion it conforms to acceptable 
standards of scholarly presentation and is fully adequate, in scope and quality, as a 
dissertation for the degree of Doctor of Philosophy. 

Lee R. McDowell 
Professor of Animal Science 



I certify that I have read this study and that in irnys opinion it conforms to acceptable 
standards of scholarly presentation and is fuhV-ads^iate, in scope and quality, as a 
dissertation for the degree of Doctor of Rhlf '* 




-Ellis C. Oreiner 
Professor of Veterinary Medicine 



This dissertation was submitted to the Graduate Faculty of the College of Agriculture and to 
the Graduate School and was accepted as partial fulfillment of the requirements for the 
degree of Doctor of Philosophy. 



May 1998 




<£&4u 




Dean, College of Agriculture 



Dean, Graduate School 



LD 

1780 

199£ 



UNIVERSITY OF FLORIDA 



3 1262 08555 1124